BUG: Fix Timestamp type checks to work with subclassed datetime (#25851)

doc/source/whatsnew/v0.25.0.rst

@@ -325,7 +325,7 @@ Sparse
 Other
 ^^^^^
 
--
+- Improved :class:`Timestamp` type checking in various datetime functions to prevent exceptions when using a subclassed `datetime` (:issue:`25851`)
 -
 -
 

pandas/_libs/tslib.pyx

@@ -2,7 +2,6 @@
 import cython
 
 from cpython.datetime cimport (PyDateTime_Check, PyDate_Check,
- PyDateTime_CheckExact,
  PyDateTime_IMPORT,
  timedelta, datetime, date, time)
 # import datetime C API
@@ -19,6 +18,7 @@ import pytz
 from pandas._libs.util cimport (
  is_integer_object, is_float_object, is_string_object, is_datetime64_object)
 
+from pandas._libs.tslibs._timestamp cimport _Timestamp
 
 from pandas._libs.tslibs.np_datetime cimport (
  check_dts_bounds, npy_datetimestruct, _string_to_dts, dt64_to_dtstruct,
@@ -539,8 +539,7 @@ cpdef array_to_datetime(ndarray[object] values, str errors='raise',
  'datetime64 unless utc=True')
  else:
  iresult[i] = pydatetime_to_dt64(val, &dts)
- if not PyDateTime_CheckExact(val):
- # i.e. a Timestamp object
+ if isinstance(val, _Timestamp):
  iresult[i] += val.nanosecond
  check_dts_bounds(&dts)
 

pandas/_libs/tslibs/_timestamp.pxd

@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+
+from cpython.datetime cimport datetime
+
+from numpy cimport int64_t
+
+cdef class _Timestamp(datetime):
+ cdef readonly:
+ int64_t value, nanosecond
+ object freq
+ list _date_attributes
+ cpdef bint _get_start_end_field(self, str field)
+ cpdef _get_date_name_field(self, object field, object locale)
+ cdef int64_t _maybe_convert_value_to_local(self)
+ cpdef to_datetime64(self)
+ cdef _assert_tzawareness_compat(_Timestamp self, datetime other)
+ cpdef datetime to_pydatetime(_Timestamp self, bint warn=*)
+ cdef bint _compare_outside_nanorange(_Timestamp self, datetime other,
+ int op) except -1